THREATS AND RESPONSES: THE MILITARY; U.S. Is Striking Iraqi Missiles Near Kuwait

Iraq has placed surface-to-surface missiles within range of Kuwait in recent weeks, prompting a series of American airstrikes and opening a new phase in the low-grade air war between Iraq and the United States, according to American officials.

As the United States has prepared for a potential war with Iraq, the main focus of its airstrikes has been disabling Iraq air defenses. The attacks, which have been carried out with increasing frequency, have usually been intended to enforce the no-flight zones over southern and northern Iraq and to make it easier for the United States to achieve air superiority quickly if a war begins.

But in recent weeks, there has been a new category of targets: Iraq's surface-to-surface missiles and rockets, systems that could threaten an American-led invasion force, American allies like Kuwait, and Iraqi opponents of President Saddam Hussein.

Iraq seems to be trying to put in place an ability to hit American forces, slowing any attack, and to threaten Kuwait. For its part, the United States seems determined to strike any missiles it finds in the south or the north to ensure that an attack could be swift, decisive and uninterrupted.

Because Iraq's missiles are mobile and have sufficient range to reach Kuwait City, attacking them is also an important gesture to the Kuwaiti government, emphasizing that the country will be defended as tensions with Iraq rise.

Most of the world's attention seems to be riveted on Iraq's decision to yield to United Nations demands that it destroy its Al Samoud 2 missiles, weapons that the United Nations says exceed the 93-mile range limit it set to restrict Iraq's offensive ability. But those missiles are not Iraq's only missiles, and they have not been the target of the recent strikes.

Rather, American and British warplanes have attacked Iraq's Ababil-100 missiles, Frog-7 rockets and an Astros 2 multiple rocket launcher. The strikes have been reported five times since Feb. 11, most recently on Tuesday, when there were four strikes on Iraqi missiles and rockets in the north and south.

The missile placements are just part of a variety of military preparations within the country. A senior Pentagon official said this week that the American military had detected ''significant movements inside Iraq.''

Iraq, for example, is repositioning its Adnan Republican Guard division by moving it from its base near Mosul toward Baghdad or Tikrit, Mr. Hussein's hometown. An Iraqi MIG-25 fighter has zoomed down to the Saudi border, one of several recent violations of the no-flight zone. That may be a way to test the American ability to defend the skies over Saudi Arabia and other gulf states as well as a means of trying to signal to the Saudis what might be in store for them if they cooperate with the American invasion plans.

But the deployment of Iraq's surface-to-surface missiles is a growing concern for the American military, and one that American officials assert violates Security Council resolutions concluded after the Persian Gulf war 12 years ago.

''They have moved some of their short-range, surface-to-surface missiles to the north and to the south,'' the senior Pentagon official said. He described the missiles as ''an immediate potential danger to us and our allies and the coalition in the region.''

The Ababil-100 is one of Iraq's newest systems, and it is under study by the United Nations. The Central Intelligence Agency says the Ababil-100 has a longer range than the 93-mile limit permitted by the United Nations. Work on the engine is carried out at Iraq's Al Mutasim site. The British Defense Ministry says the missile's solid fuel makes the system easier to handle than the Samoud 2, which uses a liquid propellant.

Once fielded, the Ababil-100 is mounted on a truck. According to some accounts, it has a warhead that can dispense antitank bomblets or mines.

But a greater concern is that it might be outfitted with a chemical or biological warhead. American intelligence has reported that Mr. Hussein has authorized his commanders to use chemical and perhaps biological weapons. It is not clear, however, whether the Ababil-100 missiles have been deployed with such warheads.

What is clear is that the United States has reacted quickly after detecting them. On Feb. 11 and 12, airstrikes hit two Ababil-100 systems in Basra that American officials said had the range to hit American troops and targets in Kuwait, the key staging area for the main American-led invasion force. On Feb. 18, another strike was carried out against another Ababil-100 system in the Basra area.

Feb. 25 was a big day. On that day, a bombing raid was carried out in the south against an Astros 2 multiple rocket launcher, which is mounted on the back of a truck. In the north, allied planes attacked three Frog rocket systems, a Soviet-designed short-range weapon, that were deployed six miles south of Mosul. Iraq has also placed Ababil-50 and Ababil-100 missiles north of Baghdad.

American officials believe the missiles have been put in place to strengthen Iraq's defenses in the north and to threaten population centers like Kirkuk and Mosul if the Americans or Kurdish forces capture the cities.

The American airstrikes came on the heels of a Jan. 13 strike near Basra against an Iraqi antiship missile launcher, which the American military said could have threatened allied ships in the Persian Gulf. That episode was another indication that Iraq was trying to make defensive preparations and that the American military was equally determined to thwart them.

The airstrikes are not being cast as just a means of enforcing the no-flight zones. Rather, the United States has justified them on the basis of United Nations resolutions that were meant to prevent Iraq from building up its offensive ability and threatening its neighbors. The strikes in the south have been pegged to United Nations Security Council Resolution 949, which prohibited Iraq from enhancing its military capacity in the south.

Lord Robertson, the NATO secretary general, cited the deployment of the Ababil-100 during NATO's private deliberations last month as he sought to persuade NATO to send Awacs radar planes and Patriot antimissile systems to Turkey, according to a NATO official.

Beyond the legal arguments and alliance politics, however, the Iraqi deployment of the missiles and the allied counterblows appear to be part of the process of shaping the battlefield for a war that seems increasingly likely to come.